1. Field of the Invention
The present invention relates to a digital .gamma. correction circuit that performs .gamma. correction on digital brightness data and digital density data corresponding to the .gamma. characteristics of LCDS, scanners, printers and so forth. Moreover, the present invention relates to an image data processing apparatus equipped with this type of .gamma. correction circuit, contrast control circuit, brightness control circuit and so forth.
2. Description of the Prior Art
Known methods employed in the form of this type of digital .gamma. correction circuit of the prior art include a method wherein converted values corresponding to the .gamma. characteristics of an LCD, scanner, printer and so forth were stored in ROM in advance, after which digital brightness data or digital density data prior to correction was applied to ROM in the form of an address to perform .gamma. correction, and a method wherein digital brightness data or digital density data X prior to correction was divided into a plurality of regions, after which an operation was performed on each region by an arithmetic processing circuit according to the following formula to perform .gamma. correction.
Y=AX+B
where, Y is the output value and A is the slope of the crossover line for .gamma. correction of each individual region.
However, in the method that uses ROM, increasing the number of correction curves requires a corresponding increase in the number of ROM, thereby resulting in problems such as increased costs and increased circuit area. Similarly, in the method that uses an arithmetic processing circuit, increasing the number of crossover lines for .gamma. correction results in an increase in circuit size as well as longer processing time.